package org.bouncycastle.asn1;

import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.SimpleTimeZone;
import java.util.TimeZone;

/**
 * Generalized time object.
 */
public class DERGeneralizedTime extends ASN1Object {
    String time;

    /**
     * return a generalized time from the passed in object
     * 
     * @exception IllegalArgumentException
     *                if the object cannot be converted.
     */
    public static DERGeneralizedTime getInstance(Object obj) {
        if (obj == null || obj instanceof DERGeneralizedTime) {
            return (DERGeneralizedTime) obj;
        }

        if (obj instanceof ASN1OctetString) {
            return new DERGeneralizedTime(((ASN1OctetString) obj).getOctets());
        }

        throw new IllegalArgumentException("illegal object in getInstance: " + obj.getClass().getName());
    }

    /**
     * return a Generalized Time object from a tagged object.
     * 
     * @param obj
     *            the tagged object holding the object we want
     * @param explicit
     *            true if the object is meant to be explicitly tagged false otherwise.
     * @exception IllegalArgumentException
     *                if the tagged object cannot be converted.
     */
    public static DERGeneralizedTime getInstance(ASN1TaggedObject obj, boolean explicit) {
        return getInstance(obj.getObject());
    }

    /**
     * The correct format for this is YYYYMMDDHHMMSS[.f]Z, or without the Z for local time, or Z+-HHMM on the end, for difference between local time
     * and UTC time. The fractional second amount f must consist of at least one number with trailing zeroes removed.
     * 
     * @param time
     *            the time string.
     * @exception IllegalArgumentException
     *                if String is an illegal format.
     */
    public DERGeneralizedTime(String time) {
        this.time = time;
        try {
            this.getDate();
        } catch (ParseException e) {
            throw new IllegalArgumentException("invalid date string: " + e.getMessage());
        }
    }

    /**
     * base constructer from a java.util.date object
     */
    public DERGeneralizedTime(Date time) {
        SimpleDateFormat dateF = new SimpleDateFormat("yyyyMMddHHmmss'Z'");

        dateF.setTimeZone(new SimpleTimeZone(0, "Z"));

        this.time = dateF.format(time);
    }

    DERGeneralizedTime(byte[] bytes) {
        //
        // explicitly convert to characters
        //
        char[] dateC = new char[bytes.length];

        for (int i = 0; i != dateC.length; i++) {
            dateC[i] = (char) (bytes[i] & 0xff);
        }

        this.time = new String(dateC);
    }

    /**
     * Return the time.
     * 
     * @return The time string as it appeared in the encoded object.
     */
    public String getTimeString() {
        return time;
    }

    /**
     * return the time - always in the form of YYYYMMDDhhmmssGMT(+hh:mm|-hh:mm).
     * <p>
     * Normally in a certificate we would expect "Z" rather than "GMT", however adding the "GMT" means we can just use:
     * 
     * <pre>
     * dateF = new SimpleDateFormat(&quot;yyyyMMddHHmmssz&quot;);
     * </pre>
     * 
     * To read in the time and get a date which is compatible with our local time zone.
     */
    public String getTime() {
        //
        // standardise the format.
        //
        if (time.charAt(time.length() - 1) == 'Z') {
            return time.substring(0, time.length() - 1) + "GMT+00:00";
        } else {
            int signPos = time.length() - 5;
            char sign = time.charAt(signPos);
            if (sign == '-' || sign == '+') {
                return time.substring(0, signPos) + "GMT" + time.substring(signPos, signPos + 3) + ":" + time.substring(signPos + 3);
            } else {
                signPos = time.length() - 3;
                sign = time.charAt(signPos);
                if (sign == '-' || sign == '+') {
                    return time.substring(0, signPos) + "GMT" + time.substring(signPos) + ":00";
                }
            }
        }
        return time + calculateGMTOffset();
    }

    private String calculateGMTOffset() {
        String sign = "+";
        TimeZone timeZone = TimeZone.getDefault();
        int offset = timeZone.getRawOffset();
        if (offset < 0) {
            sign = "-";
            offset = -offset;
        }
        int hours = offset / (60 * 60 * 1000);
        int minutes = (offset - (hours * 60 * 60 * 1000)) / (60 * 1000);

        try {
            if (timeZone.useDaylightTime() && timeZone.inDaylightTime(this.getDate())) {
                hours += sign.equals("+") ? 1 : -1;
            }
        } catch (ParseException e) {
            // we'll do our best and ignore daylight savings
        }

        return "GMT" + sign + convert(hours) + ":" + convert(minutes);
    }

    private String convert(int time) {
        if (time < 10) {
            return "0" + time;
        }

        return Integer.toString(time);
    }

    public Date getDate() throws ParseException {
        SimpleDateFormat dateF;
        String d = time;

        if (time.endsWith("Z")) {
            if (hasFractionalSeconds()) {
                dateF = new SimpleDateFormat("yyyyMMddHHmmss.SSSS'Z'");
            } else {
                dateF = new SimpleDateFormat("yyyyMMddHHmmss'Z'");
            }

            dateF.setTimeZone(new SimpleTimeZone(0, "Z"));
        } else if (time.indexOf('-') > 0 || time.indexOf('+') > 0) {
            d = this.getTime();
            if (hasFractionalSeconds()) {
                dateF = new SimpleDateFormat("yyyyMMddHHmmss.SSSSz");
            } else {
                dateF = new SimpleDateFormat("yyyyMMddHHmmssz");
            }

            dateF.setTimeZone(new SimpleTimeZone(0, "Z"));
        } else {
            if (hasFractionalSeconds()) {
                dateF = new SimpleDateFormat("yyyyMMddHHmmss.SSSS");
            } else {
                dateF = new SimpleDateFormat("yyyyMMddHHmmss");
            }

            dateF.setTimeZone(new SimpleTimeZone(0, TimeZone.getDefault().getID()));
        }

        return dateF.parse(d);
    }

    private boolean hasFractionalSeconds() {
        return time.indexOf('.') == 14;
    }

    private byte[] getOctets() {
        char[] cs = time.toCharArray();
        byte[] bs = new byte[cs.length];

        for (int i = 0; i != cs.length; i++) {
            bs[i] = (byte) cs[i];
        }

        return bs;
    }

    void encode(DEROutputStream out) throws IOException {
        out.writeEncoded(GENERALIZED_TIME, this.getOctets());
    }

    boolean asn1Equals(DERObject o) {
        if (!(o instanceof DERGeneralizedTime)) {
            return false;
        }

        return time.equals(((DERGeneralizedTime) o).time);
    }

    public int hashCode() {
        return time.hashCode();
    }
}
